Impact of biotin supplemented diet on mouse pancreatic islet β-cell mass expansion and glucose induced electrical activity

Biotin supplemented diet (BSD) is known to enhance β-cell replication and insulin secretion in mice. Here, we first describe BSD impact on the islet β-cell membrane potential (Vm) and glucose-induced electrical activity. BALB/c female mice (n ≥ 20) were fed for nine weeks after weaning with a control diet (CD) or a BSD (100X). In both groups, islet area was compared in pancreatic sections incubated with anti-insulin and anti-glucagon antibodies; Vm was recorded in micro dissected islet β-cells during perfusion with saline solutions containing 2.8, 5.0, 7.5-, or 11.0 mM glucose. BSD increased the islet and β-cell area compared with CD. In islet β-cells of the BSD group, a larger ΔVm/Δ[glucose] was found at sub-stimulatory glucose concentrations and the threshold glucose concentration for generation of action potentials (APs) was increased by 1.23 mM. Moreover, at 11.0 mM glucose, a significant decrease was found in AP amplitude, frequency, ascending and descending slopes as well as in the calculated net charge influx and efflux of islet β-cells from BSD compared to the CD group, without changes in slow Vm oscillation parameters. A pharmacological dose of biotin in mice increases islet insulin cell mass, shifts islet β-cell intracellular electrical activity dose response curve toward higher glucose concentrations, very likely by increasing K_ATP conductance, and decreases voltage gated Ca²⁺ and K⁺ conductance at stimulatory glucose concentrations.

Formation of Re-Aggregated Neonatal Porcine Islet Clusters Improves In Vitro Function and Transplantation Outcome

Neonatal porcine islet-like cell clusters (NPICCs) are a promising source for islet cell transplantation. Excellent islet quality is important to achieve a cure for type 1 diabetes. We investigated formation of cell clusters from dispersed NPICCs on microwell cell culture plates, evaluated the composition of re-aggregated porcine islets (REPIs) and compared in vivo function by transplantation into diabetic NOD-SCID IL2rγ-/- (NSG) mice with native NPICCs. Dissociation of NPICCs into single cells and re-aggregation resulted in the formation of uniform REPI clusters. A higher prevalence of normoglycemia was observed in diabetic NSG mice after transplantation with a limited number (n = 1500) of REPIs (85.7%) versus NPICCs (n = 1500) (33.3%) (p < 0.05). Transplanted REPIs and NPICCs displayed a similar architecture of endocrine and endothelial cells. Intraperitoneal glucose tolerance tests revealed an improved beta cell function after transplantation of 1500 REPIs (AUC glucose 0-120 min 6260 ± 305.3) as compared to transplantation of 3000 native NPICCs (AUC glucose 0-120 min 8073 ± 536.2) (p < 0.01). Re-aggregation of single cells from dissociated NPICCs generates cell clusters with excellent functionality and improved in vivo function as compared to native NPICCs.

Dynamic Ins2 Gene Activity Defines β-Cell Maturity States

Transcriptional and functional cellular specialization has been described for insulin-secreting β-cells of the endocrine pancreas. However, it is not clear whether β-cell heterogeneity is stable or reflects dynamic cellular states. We investigated the temporal kinetics of endogenous insulin gene activity using live cell imaging, with complementary experiments using FACS and single-cell RNA sequencing, in β-cells from Ins2GFP knockin mice. In vivo staining and FACS analysis of islets from Ins2GFP mice confirmed that at a given moment, ∼25% of β-cells exhibited significantly higher activity at the evolutionarily conserved insulin gene, Ins2. Live cell imaging over days captured Ins2 gene activity dynamics in single β-cells. Autocorrelation analysis revealed a subset of oscillating cells, with mean oscillation periods of 17 h. Increased glucose concentrations stimulated more cells to oscillate and resulted in higher average Ins2 gene activity per cell. Single-cell RNA sequencing showed that Ins2(GFP)HIGH β-cells were enriched for markers of β-cell maturity. Ins2(GFP)HIGH β-cells were also significantly less viable at all glucose concentrations and in the context of endoplasmic reticulum stress. Collectively, our results demonstrate that the heterogeneity of insulin production, observed in mouse and human β-cells, can be accounted for by dynamic states of insulin gene activity.

Islet Autoantibody Levels Differentiate Progression Trajectories in Individuals With Presymptomatic Type 1 Diabetes

In our previous data-driven analysis of evolving patterns of islet autoantibodies (IAb) against insulin (IAA), GAD (GADA), and islet antigen 2 (IA-2A), we discovered three trajectories, characterized according to multiple IAb (TR1), IAA (TR2), or GADA (TR3) as the first appearing autoantibodies. Here we examined the evolution of IAb levels within these trajectories in 2,145 IAb-positive participants followed from early life and compared those who progressed to type 1 diabetes (n = 643) with those remaining undiagnosed (n = 1,502). With use of thresholds determined by 5-year diabetes risk, four levels were defined for each IAb and overlaid onto each visit. In diagnosed participants, high IAA levels were seen in TR1 and TR2 at ages <3 years, whereas IAA remained at lower levels in the undiagnosed. Proportions of dwell times (total duration of follow-up at a given level) at the four IAb levels differed between the diagnosed and undiagnosed for GADA and IA-2A in all three trajectories (P < 0.001), but for IAA dwell times differed only within TR2 (P < 0.05). Overall, undiagnosed participants more frequently had low IAb levels and later appearance of IAb than diagnosed participants. In conclusion, while it has long been appreciated that the number of autoantibodies is an important predictor of type 1 diabetes, consideration of autoantibody levels within the three autoimmune trajectories improved differentiation of IAb-positive children who progressed to type 1 diabetes from those who did not.

Optimizing Generation of Stem Cell-Derived Islet Cells

Islet transplantation is a highly effective treatment for select patients with type 1 diabetes. Unfortunately, current use is limited to those with brittle disease due to donor limitations and immunosuppression requirements. Discovery of factors for induction of pluripotent stem cells from adult somatic cells into a malleable state has reinvigorated the possibility of autologous-based regenerative cell therapies. Similarly, recent progress in allogeneic human embryonic stem cell islet products is showing early success in clinical trials. Describing safe and standardized differentiation protocols with clear pathways to optimize yield and minimize off-target growth is needed to efficiently move the field forward. This review discusses current islet differentiation protocols with a detailed break-down of differentiation stages to guide step-wise controlled generation of functional islet products.

Infections in the first year of life and development of beta cell autoimmunity and clinical type 1 diabetes in high-risk individuals: the TRIGR cohort

AIMS/HYPOTHESIS

Accumulated data suggest that infections in early life contribute to the development of type 1 diabetes. Using data from the Trial to Reduce IDDM in the Genetically at Risk (TRIGR), we set out to assess whether children who later developed diabetes-related autoantibodies and/or clinical type 1 diabetes had different exposure to infections early in life compared with those who did not.

METHODS

A cohort of 2159 children with an affected first-degree relative and HLA-conferred susceptibility to type 1 diabetes were recruited between 2002 and 2007 and followed until 2017. Infections were registered prospectively. The relationship between infections in the first year of life and the development of autoantibodies or clinical type 1 diabetes was analysed using univariable and multivariable Cox regression models. As this study was exploratory, no adjustment was made for multiple comparisons.

RESULTS

Adjusting for HLA, sex, breastfeeding duration and birth order, those who had seven or more infections during their first year of life were more likely to develop at least one positive type 1 diabetes-related autoantibody (p=0.028, HR 9.166 [95% CI 1.277, 65.81]) compared with those who had no infections. Those who had their first viral infection aged between 6 and 12 months were less likely to develop at least one positive type 1 diabetes-related antibody (p=0.043, HR 0.828 [95% CI 0.690, 0.994]) or multiple antibodies (p=0.0351, HR 0.664 [95% CI 0.453, 0.972]). Those who had ever had an unspecified bacterial infection were more likely to develop at least one positive type 1 diabetes-related autoantibody (p=0.013, HR 1.412 [95% CI 1.075, 1.854]), to develop multiple antibodies (p=0.037, HR 1.652 [95% CI 1.030, 2.649]) and to develop clinical type 1 diabetes (p=0.011, HR 2.066 [95% CI 1.182, 3.613]).

CONCLUSIONS/INTERPRETATION

We found weak support for the assumption that viral infections early in life may initiate the autoimmune process or later development of type 1 diabetes. In contrast, certain bacterial infections appeared to increase the risk of both multiple autoantibodies and clinical type 1 diabetes.

Efficacy of a new enzyme-linked immunosorbent assay system for three islet cell autoantibodies in Japanese patients with acute-onset type 1 diabetes

To evaluate the clinical efficacy of a new enzyme-linked immunosorbent assay (ELISA) system for simultaneously detecting three islet cell autoantibodies against glutamic acid decarboxylase (GADA), insulinoma-associated antigen-2 (IA-2A), and zinc transporter 8 (ZnT8A) (3 Screen ICA ELISA) in Japanese patients with acute-onset type 1 diabetes (T1D). In addition, clinical factors affecting the 3 Screen ICA ELISA index were investigated. We compared the positivity values of 3 Screen ICA ELISA with that of each autoantibody alone in 97 patients with acute-onset T1D (mean age 48.7 years, 49% male) and 100 non-diabetic subjects (mean age 47.0 years, 50% male). Serum thyroid stimulating hormone receptor antibody, thyroid peroxidase antibody (TPOAb) and thyroglobulin autoantibody levels were also evaluated. The cut-off value of the 3 Screen ICA ELISA was determined based on the 97^th percentile of 100 non-diabetic controls (threshold for positivity, ≥14 index). The mean age of disease onset and duration of diabetes were 34.2 years and 14.5 years, respectively. Among all T1D patients, the positivity of 3 Screen ICA ELISA was 71.1%, while that of GADA, IA-2A, and ZnT8A were 59.8%, 25.8%, and 25.8%, respectively. The median 3 Screen ICA index was 121.9 (8.7-468.2) and was associated with titers of each autoantibody, most so with GADA, and was significantly higher in TPOAb-positive patients than in TPOAb-negative patients. Our findings suggests that the 3 Screen ICA ELISA may be a time-saving diagnostic tool for evaluating islet autoantibodies in acute-onset T1D patients.

Pathophysiology of Type 1 Diabetes and Gut Microbiota Role

Type 1 diabetes (T1D) is a multifactorial autoimmune disease driven by T-cells against the insulin-producing islet β-cells, resulting in a marked loss of β-cell mass and function. Although a genetic predisposal increases susceptibility, the role of epigenetic and environmental factors seems to be much more significant. A dysbiotic gut microbial profile has been associated with T1D patients. Moreover, new evidence propose that perturbation in gut microbiota may influence the T1D onset and progression. One of the prominent features in clinically silent phase before the onset of T1D is the presence of a microbiota characterized by low numbers of commensals butyrate producers, thus negatively influencing the gut permeability. The loss of gut permeability leads to the translocation of microbes and microbial metabolites and could lead to the activation of immune cells. Moreover, microbiota-based therapies to slow down disease progression or reverse T1D have shown promising results. Starting from this evidence, the correction of dysbiosis in early life of genetically susceptible individuals could help in promoting immune tolerance and thus in reducing the autoantibodies production. This review summarizes the associations between gut microbiota and T1D for future therapeutic perspectives and other exciting areas of research.

Microwell culture platform maintains viability and mass of human pancreatic islets

Background

Transplantation of the human pancreatic islets is a promising approach for specific types of diabetes to improve glycemic control. Although effective, there are several issues that limit the clinical expansion of this treatment, including difficulty in maintaining the quality and quantity of isolated human islets prior to transplantation. During the culture, we frequently observe the multiple islets fusing together into large constructs, in which hypoxia-induced cell damage significantly reduces their viability and mass. In this study, we introduce the microwell platform optimized for the human islets to prevent unsolicited fusion, thus maintaining their viability and mass in long-term cultures.

Method

Human islets are heterogeneous in size; therefore, two different-sized microwells were prepared in a 35 mm-dish format: 140 µm × 300 µm-microwells for <160 µm-islets and 200 µm × 370 µm-microwells for >160 µm-islets. Human islets (2,000 islet equivalent) were filtered through a 160 µm-mesh to prepare two size categories for subsequent two week-cultures in each microwell dish. Conventional flat-bottomed 35 mm-dishes were used for non-filtered islets (2,000 islet equivalent/2 dishes). Post-cultured islets are collected to combine in each condition (microwells and flat) for the comparisons in viability, islet mass, morphology, function and metabolism. Islets from three donors were independently tested.

Results

The microwell platform prevented islet fusion during culture compared to conventional flat bottom dishes, which improved human islet viability and mass. Islet viability and mass on the microwells were well-maintained and comparable to those in pre-culture, while flat bottom dishes significantly reduced islet viability and mass in two weeks. Morphology assessed by histology, insulin-secreting function and metabolism by oxygen consumption did not exhibit the statistical significance among the three different conditions.

Conclusion

Microwell-bottomed dishes maintained viability and mass of human islets for two weeks, which is significantly improved when compared to the conventional flat-bottomed dishes.

Multiplexed microfluidic platform for stem-cell derived pancreatic islet β cells

Stem cell-derived β cells offer an alternative to primary islets for biomedical discoveries as well as a potential surrogate for islet transplantation. The expense and challenge of obtaining and maintaining functional stem cell-derived β cells calls for a need to develop better high-content and high-throughput culture systems. Microphysiological systems (MPS) are promising high-content in vitro platforms, but scaling for high-throughput screening and discoveries remain a challenge. Traditionally, simultaneous multiplexing of liquid handling and cell loading poses a challenge in the design of high-throughput MPS. Furthermore, although MPS for islet β culture/testing have been developed, studies on multi-day culture of stem-cell derived β cells in MPS have been limited. We present a scalable, multiplexed islet β MPS device that incorporates microfluidic gradient generators to parallelize fluid handling for culture and test conditions. We demonstrated the viability and functionality of the stem cell-derived enriched β clusters (eBCs) for a week, as assessed by the ∼2 fold insulin release by the clusters to glucose challenge. To show the scalable multiplexing for drug testing, we demonstrated the loss of stimulation index after long-term exposure to logarithmic concentration range of glybenclamide. The MPS cultured eBCs also confirmed a glycolytic bottleneck as inferred by insulin secretion responses to metabolites methyl succinate and glyceric acid. Thus, we present an innovative culture platform for eBCs with a balance of high-content and high-throughput characteristics.

The continuous spectrum of glycaemic variability changes with pancreatic islet function: A multicentre cross-sectional study in China

AIMS

To investigate glycaemic variability (GV) patterns in patients with type 1 diabetes (T1D), type 2 diabetes (T2D), and latent autoimmune diabetes in adults (LADA).

MATERIALS AND METHODS

A total of 842 subjects (510 T1D, 105 LADA, 227 T2D) were enrolled and underwent 1 week of continuous glucose monitoring (CGM). Clinical characteristics and CGM parameters were compared among T1D, LADA, and T2D. LADA patients were divided into two subgroups based on glutamic acid decarboxylase autoantibody titres (≥180 U/mL [LADA-1], <180 U/mL [LADA-2]) and compared. The C-peptide cut-offs for predicting a coefficient of variation (CV) of glucose ≥36% and a time in range (TIR) > 70% were determined using receiver operating characteristic analysis.

RESULTS

Twenty-seven patients (9 T1D, 18 T2D) were excluded due to insufficient CGM data. Sex, diabetes duration and HbA1c were comparable among the three groups. Fasting and 2-h postprandial C-peptide (FCP, 2hCP) increased sequentially across T1D, LADA, and T2D. T1D and LADA patients had comparable TIR and GV, whereas those with T2D had much higher TIR and lower GV (p < 0.001). The GV of LADA-1 was close to that of T1D, while the GV of LADA-2 was close to that of T2D. CP exhibited the strongest negative correlation with GV. The cut-offs of FCP/2hCP for predicting a CV ≥ 36% and TIR >70% were 121.6/243.1 and 128.9/252.8 pmol/L, respectively.

CONCLUSIONS

GV presented a continuous spectrum across T1D, LADA-1, LADA-2, and T2D. More frequent glucose monitoring is suggested for patients with impaired insulin secretion.

CLINICAL TRAIL REGISTRATION

Chinese Clinical Trial Registration (ChiCTR) website approved by WHO; http://www.chictr.org.cn/ - ChiCTR2200065036.

Transcriptome reveals the dysfunction of pancreatic islets after wound healing in severely burned mice

BACKGROUND

Severely burned patients have a higher risk of diabetes mellitus after healing, but its mechanism remains unclear. Therefore, the purpose of the study was to explore the influence of burns on pancreatic islets of mice after wound healing.

METHODS

Forty-two male C57BL/6 mice were randomized into a sham group and a burn group and subjected to sham treatment or a third-degree burn model of 30% total body surface area. Fasting blood glucose was detected weekly for 8 weeks after severe burns. Glucose-stimulated insulin secretion was measured 8 weeks post severe burns. Islets of the two groups were isolated and mRNA libraries were sequenced by the Illumina sequencing platform. The expressions of differentially expressed genes (DEGs) related to the cell cycle and the amounts of mitochondrial DNA were detected by quantitative real-time polymerase chain reaction after gene ontology, gene set enrichment analysis, and protein-protein network analysis. Hematoxylin-eosin staining of pancreatic tail tissue and adenosine triphosphate (ATP) assay of islets were performed.

RESULTS

The levels of fasting blood glucose were significantly higher within 8 weeks post severe burns. Glucose-stimulated insulin secretion was impaired at the eighth week post severe burns. Totally 128 DEGs were selected. Gene ontology and gene set enrichment analysis indicated that the pathways related to the cell cycle, protein processing, and oxidative phosphorylation were downregulated. The expressions of DEGs related to the cell cycle showed a consistent trend with mRNA sequencing data, and most of them were downregulated post severe burns. The cell mass of the burn group was less than that of the sham group. Also, the concentration of ATP and the amount of mitochondrial DNA were lower in the burn group.

CONCLUSION

In the model of severe-burned mice, disorders in glucose metabolism persist for 8 weeks after burns, which may be related to low islet cell proliferation, downregulation of protein processing, and less ATP production.

Elevations in blood glucose before and after the appearance of islet autoantibodies in children

The etiology of type 1 diabetes has polygenic and environmental determinants that lead to autoimmune responses against pancreatic β cells and promote β cell death. The autoimmunity is considered silent without metabolic consequences until late preclinical stages,and it remains unknown how early in the disease process the pancreatic β cell is compromised. To address this, we investigated preprandial nonfasting and postprandial blood glucose concentrations and islet autoantibody development in 1,050 children with high genetic risk of type 1 diabetes. Pre- and postprandial blood glucose decreased between 4 and 18 months of age and gradually increased until the final measurements at 3.6 years of age. Determinants of blood glucose trajectories in the first year of life included sex, body mass index, glucose-related genetic risk scores, and the type 1 diabetes–susceptible INS gene. Children who developed islet autoantibodies had early elevations in blood glucose concentrations. A sharp and sustained rise in postprandial blood glucose was observed at around 2 months prior to autoantibody seroconversion, with further increases in postprandial and, subsequently, preprandial values after seroconversion. These findings show heterogeneity in blood glucose control in infancy and early childhood and suggest that islet autoimmunity is concurrent or subsequent to insults on the pancreatic islets.

Type 1 diabetes: what is the role of autoimmunity in β cell death?

The current dogma of type 1 diabetes pathogenesis asserts that an autoimmune attack leads to the destruction of pancreatic β cells, with subsequent hyperglycemia. This dogma is based on islet autoantibodies emerging prior to the onset of type 1 diabetes. In this issue of the JCI, Warncke et al. report on their investigation of the development of hyperglycemia below the diabetes threshold as an early proxy of β cell demise. Surprisingly, they found that an elevation in blood glucose preceded the appearance of autoimmunity. This observation calls into question the importance of autoimmunity as the primary cause of β cell destruction and has implications for prevention and treatment in diabetes.

Predictors of the Initiation of Islet Autoimmunity and Progression to Multiple Autoantibodies and Clinical Diabetes: The TEDDY Study

OBJECTIVE

To distinguish among predictors of seroconversion, progression to multiple autoantibodies and from multiple autoantibodies to type 1 diabetes in young children.

RESEARCH DESIGN AND METHODS

Genetically high-risk newborns (n = 8,502) were followed for a median of 11.2 years (interquartile range 9.3-12.6); 835 (9.8%) developed islet autoantibodies and 283 (3.3%) were diagnosed with type 1 diabetes. Predictors were examined using Cox proportional hazards models.

RESULTS

Predictors of seroconversion and progression differed, depending on the type of first appearing autoantibody. Male sex, Finnish residence, having a sibling with type 1 diabetes, the HLA DR4 allele, probiotic use before age 28 days, and single nucleotide polymorphism (SNP) rs689_A (INS) predicted seroconversion to IAA-first (having islet autoantibody to insulin as the first appearing autoantibody). Increased weight at 12 months and SNPs rs12708716_G (CLEC16A) and rs2292239_T (ERBB3) predicted GADA-first (autoantibody to GAD as the first appearing). For those having a father with type 1 diabetes, the SNPs rs2476601_A (PTPN22) and rs3184504_T (SH2B3) predicted both. Younger age at seroconversion predicted progression from single to multiple autoantibodies as well as progression to diabetes, except for those presenting with GADA-first. Family history of type 1 diabetes and the HLA DR4 allele predicted progression to multiple autoantibodies but not diabetes. Sex did not predict progression to multiple autoantibodies, but males progressed more slowly than females from multiple autoantibodies to diabetes. SKAP2 and MIR3681HG SNPs are newly reported to be significantly associated with progression from multiple autoantibodies to type 1 diabetes.

CONCLUSIONS

Predictors of IAA-first versus GADA-first autoimmunity differ from each other and from the predictors of progression to diabetes.

Abnormal Expression of an Insulin Synthesizing Enzyme in Islets of Adult Autoantibody Positive Donors

The observation that the two active forms of proprotein convertase 1/3 (PC1/3) were differentially expressed in beta cells of normal islets raised the possibility that this heterogeneity is lost during type 1 diabetes (T1D) progression. To test this hypothesis, the expression of the convertase was evaluated by confocal microscopy in sections of human pancreas of autoantibody positive (AA+) and T1D donors and compared with that of control. Islets of T1D pancreas were comprised of beta cells expressing either low or high PC1/3 levels and all islets of a pancreatic section contained only one beta cell type. Pancreata of AA+ donors contained either of these two classes of islets intermixed with normal islets comprised of beta cells with heterogeneous PC1/3 expression. This alteration affected the expression of proinsulin and insulin, which in most AA+ and T1D donors were lower than in controls. The present results indicate that the heterogeneity of PC1/3 expression is lost in all beta cells in a subset islets of AA+ donors and in all islets of T1D donors. These findings suggest that the heterogeneity of PC1/3 expression is a biomarker of human beta cell health and that its loss coincides with the initial stages of T1D.

The role of GABA in islet function

Gamma aminobutyric acid (GABA) is a non-proteinogenic amino acid and neurotransmitter that is produced in the islet at levels as high as in the brain. GABA is synthesized by the enzyme glutamic acid decarboxylase (GAD), of which the 65 kDa isoform (GAD65) is a major autoantigen in type 1 diabetes. Originally described to be released via synaptic-like microvesicles or from insulin secretory vesicles, beta cells are now understood to release substantial quantities of GABA directly from the cytosol via volume-regulated anion channels (VRAC). Once released, GABA influences the activity of multiple islet cell types through ionotropic GABAA receptors and metabotropic GABAB receptors. GABA also interfaces with cellular metabolism and ATP production via the GABA shunt pathway. Beta cells become depleted of GABA in type 1 diabetes (in remaining beta cells) and type 2 diabetes, suggesting that loss or reduction of islet GABA correlates with diabetes pathogenesis and may contribute to dysfunction of alpha, beta, and delta cells in diabetic individuals. While the function of GABA in the nervous system is well-understood, the description of the islet GABA system is clouded by differing reports describing multiple secretion pathways and effector functions. This review will discuss and attempt to unify the major experimental results from over 40 years of literature characterizing the role of GABA in the islet.

Liraglutide protects β-cells in novel human islet spheroid models of type 1 diabetes

To enable accurate, high-throughput and longer-term studies of the immunopathogenesis of type 1 diabetes (T1D), we established three in-vitro islet-immune injury models by culturing spheroids derived from primary human islets with proinflammatory cytokines, activated peripheral blood mononuclear cells or HLA-A2-restricted preproinsulin-specific cytotoxic T lymphocytes. In all models, β-cell function declined as manifested by increased basal and decreased glucose-stimulated insulin release (GSIS), and decreased intracellular insulin content. Additional hallmarks of T1D progression such as loss of the first-phase insulin response (FFIR), increased proinsulin-to-insulin ratios, HLA-class I expression, and inflammatory cytokine release were also observed. Using these models, we show that liraglutide, a glucagon-like peptide 1 receptor agonist, prevented loss of GSIS under T1D-relevant stress, by preserving the FFIR and decreasing immune cell infiltration and cytokine secretion. Our results corroborate that liraglutide mediates an anti-inflammatory effect that aids in protecting β-cells from the immune-mediated attack that leads to T1D.

Differentiation of Microencapsulated Neonatal Porcine Pancreatic Cell Clusters in Vitro Improves Transplant Efficacy in Type 1 Diabetes Mellitus Mice

BACKGROUND

Neonatal porcine pancreatic cell clusters (NPCCs) have been proposed as an alternative source of β cells for islet transplantation because of their low cost and growth potential after transplantation. However, the delayed glucose lowering effect due to the immaturity of NPCCs and immunologic rejection remain as a barrier to NPCC's clinical application. Here, we demonstrate accelerated differentiation and immune-tolerant NPCCs by in vitro chemical treatment and microencapsulation.

METHODS

NPCCs isolated from 3-day-old piglets were cultured in F-10 media and then microencapsulated with alginate on day 5. Differentiation of NPCCs is facilitated by media supplemented with activin receptor-like kinase 5 inhibitor II, triiodothyronine and exendin-4 for 2 weeks. Marginal number of microencapsulated NPCCs to cure diabetes with and without differentiation were transplanted into diabetic mice and observed for 8 weeks.

RESULTS

The proportion of insulin-positive cells and insulin mRNA levels of NPCCs were significantly increased in vitro in the differentiated group compared with the undifferentiated group. Blood glucose levels decreased eventually after transplantation of microencapsulated NPCCs in diabetic mice and normalized after 7 weeks in the differentiated group. In addition, the differentiated group showed nearly normal glucose tolerance at 8 weeks after transplantation. In contrast, neither blood glucose levels nor glucose tolerance were improved in the undifferentiated group. Retrieved graft in the differentiated group showed greater insulin response to high glucose compared with the undifferentiated group.

CONCLUSION

in vitro differentiation of microencapsulated immature NPCCs increased the proportion of insulin-positive cells and improved transplant efficacy in diabetic mice without immune rejection.

Co-transplantation of Islets-Laden Microgels and Biodegradable O2-Generating Microspheres for Diabetes Treatment

Pancreatic islets transplantation is an optimal alternative to exogenous insulin injection for long-term effective type 1 diabetes treatment. However, direct islets transplantation without any protection can induce cell necrosis due to severe host immune rejection. Insufficient O₂ supply induced by the lack of capillary network at the early stage of islets transplantation is another critical constraint limiting islets survival and insulin-secretion function. In this paper, we design a novel co-transplantation system composed of islets-laden nanocomposite microgels and O₂-generating microspheres. In particular, nanocomposite microgels confer the encapsulated islets with simultaneous physical protection and chemical anti-inflammation/immunosuppression by covalently anchoring rapamycin-loaded cyclodextrin nanoparticles to microgel network. Meanwhile, O₂-generating microspheres prepared by blending inorganic peroxides in biodegradable polycaprolactone and polylactic acid can generate in situ O₂ gas and thus avoid hypoxia environment around transplanted islets. In vivo therapeutic effect of diabetic mice proves the reversion of the high blood glucose level back to normoglycemia and superior glucose tolerance for at least 90 days post co-transplantation. In brief, the localized drug and oxygen codelivery, as well as physical protection provided by our co-transplantation system, has the potential to overcome to a large extent the inflammatory, hypoxia, and host immune rejection after islets transplantation. This new strategy may have wider application in other cell replacement therapies.

Establishment of an enzyme-linked immunosorbent assay for mouse pancreatic polypeptide clarifies the regulatory mechanism of its secretion from pancreatic γ cells

Pancreatic polypeptide (PP), secreted from γ cells of the islets of Langerhans, is a 36 amino-acid peptide encoded by the Ppy gene. Although previous studies have reported that PP causes a decrease in appetite, the molecular mechanism that regulates PP secretion has not been fully elucidated. Lack of understanding of the regulatory mechanism of PP secretion may be partially owing to the lack of assay systems that can specifically detect PP. We recently developed the mouse monoclonal antibody 23-2D3 that specifically recognizes PP. In the present study, we developed a sandwich enzyme-linked immunosorbent assay for the measurement of mouse PP, and directly monitored intracellular Ca²⁺ concentrations in Ppy-expressing cells from a newly developed reporter mouse. Using these systems, we identified agonists, such as carbachol and glucose-dependent insulinotropic polypeptide (GIP), which stimulate PP secretion. We further demonstrated that, unlike the case of GIP-induced insulin secretion from β cells, there is a unique mechanism by which PP secretion is triggered by an increase in intracellular Ca²⁺ concentrations via voltage-dependent calcium channels even in low-glucose conditions.

Application progress of nanotechnology in regenerative medicine of diabetes mellitus

In recent years, the development of diabetic regenerative medicine has led to new developments and progress for the clinical treatment of diabetes mellitus and its various complications. Besides, the emergence of nanotechnology has injected new vitality into diabetic regenerative medicine. Nano-stent provides an appropriate direction for the regeneration of islet β cells, retinal tissue, nerve tissue, and wound tissue cells. Conductive nanomaterials promote various tissues' growth. Many nanoparticles also promote wound healing and present other advantages that have solved many potential problems in the practical application of regenerative medicine. In this review, we will summarize the application of nanotechnology in diabetic regenerative medicine.

Every islet matters: improving the impact of human islet research

Detailed characterization of human pancreatic islets is key to elucidating the pathophysiology of all forms of diabetes, especially type 2 diabetes. However, access to human pancreatic islets is limited. Pancreatic tissue for islet retrieval can be obtained from brain-dead organ donors or from individuals undergoing pancreatectomy, often referred to as 'living donors'. Different protocols for human islet procurement can substantially impact islet function. This variability, coupled with heterogeneity between individuals and islets, results in analytical challenges to separate genuine disease pathology or differences between human donors from experimental noise. There are currently no international guidelines for human donor phenotyping, islet procurement and functional characterization. This lack of standardization means that substantial investments from multiple international efforts towards improved understanding of diabetes pathology cannot be fully leveraged. In this Perspective, we overview the status of the field of human islet research, highlight the challenges and propose actions that could accelerate research progress and increase understanding of type 2 diabetes to slow its pandemic spreading.

Integration of Infant Metabolite, Genetic, and Islet Autoimmunity Signatures to Predict Type 1 Diabetes by Age 6 Years

CONTEXT

Biomarkers that can accurately predict risk of type 1 diabetes (T1D) in genetically predisposed children can facilitate interventions to delay or prevent the disease.

OBJECTIVE

This work aimed to determine if a combination of genetic, immunologic, and metabolic features, measured at infancy, can be used to predict the likelihood that a child will develop T1D by age 6 years.

METHODS

Newborns with human leukocyte antigen (HLA) typing were enrolled in the prospective birth cohort of The Environmental Determinants of Diabetes in the Young (TEDDY). TEDDY ascertained children in Finland, Germany, Sweden, and the United States. TEDDY children were either from the general population or from families with T1D with an HLA genotype associated with T1D specific to TEDDY eligibility criteria. From the TEDDY cohort there were 702 children will all data sources measured at ages 3, 6, and 9 months, 11.4% of whom progressed to T1D by age 6 years. The main outcome measure was a diagnosis of T1D as diagnosed by American Diabetes Association criteria.

RESULTS

Machine learning-based feature selection yielded classifiers based on disparate demographic, immunologic, genetic, and metabolite features. The accuracy of the model using all available data evaluated by the area under a receiver operating characteristic curve is 0.84. Reducing to only 3- and 9-month measurements did not reduce the area under the curve significantly. Metabolomics had the largest value when evaluating the accuracy at a low false-positive rate.

CONCLUSION

The metabolite features identified as important for progression to T1D by age 6 years point to altered sugar metabolism in infancy. Integrating this information with classic risk factors improves prediction of the progression to T1D in early childhood.

Impacts of an Exercise Intervention on the Health of Pancreatic Beta-Cells: A Review

There is an increasing consensus that exercise is a medicine and that regular exercise can effectively improve and prevent metabolic diseases such as diabetes. Islet cells are the endocrine of the pancreas and vital to the development of diabetes. Decades of developmental research in exercise intervention and the health of islet cells confirmed that exercise exerts beneficial effects on the function, proliferation, and survival rate of islet cells. However, the precise exercise reference scheme is still elusive. To accomplish this goal, we searched and analyzed relevant articles, and concluded the precise exercise prescription treatments for various species such as humans, rats, and mice. Each exercise protocol is shown in the tables below. These exercise protocols form a rich pipeline of therapeutic development for exercise on the health of islet cells.

The evaluation of pancreas β-cell autoantibodies in non-diabetic COVID-19 patients

Objective

This study aims to evaluate potential pancreas endocrine damage due to SARS-CoV-2 by measuring β-cell autoantibodies in COVID-19 patients.

Subjects and methods

Between June and July 2020, 95 inpatients with a positive COVID-19 test result after polymerase-chain-reaction (PCR) and who met the inclusion criteria were enrolled in our study. Laboratory parameters that belong to glucose metabolism and β-cell autoantibodies, including anti-islet, anti-glutamic acid decarboxylase, and anti-insulin autoantibodies, were measured. β-cell autoantibodies levels of the patients were measured during COVID-19 diagnosis. Positive results were reevaluated in the 3rd month of control.

Results

In the initial evaluation, 4 (4.2%) patients were positive for anti-islet autoantibody. Only one (1.1%) patient was positive for anti-glutamic acid decarboxylase autoantibody. No patient had positive results for anti-insulin autoantibody. FPG, HbA1c, and C-peptide levels were similar in patients who were split into groups regarding the initial positive or negative status of anti-islet and anti-GAD autoantibodies (p>0.05). In the 3rd month after the initial measurements, anti-islet autoantibody positivity of 2 (50%) of 4 patients and anti-glutamic acid decarboxylase positivity of 1 (100%) patient were persistent. Finally, 3 (3.1%) patients in the whole group were positive for anti-islet autoantibody in the 3rd month of control. No difference was determined between the initial and the 3rd month of parameters of glucose metabolism.

Conclusion

Following an ongoing autoantibody positivity in the present study brings the mind that SARS-CoV-2 may be responsible for the diabetogenic effect. Clinicians should be aware of autoantibody-positive DM as a potential autoimmune complication in patients with SARS-CoV-2.

Small molecules released from islets of Langerhans determined by liquid chromatography - mass spectrometry

Islets of Langerhans are the endocrine tissue within the pancreas that secrete hormones for maintenance of blood glucose homeostasis. A variety of small molecules including classical neurotransmitters are also released from islets. While the roles of most of these small molecules are unknown, some have been hypothesized to play a critical role in islet physiology. To better understand their role on islet function, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to separate and quantify 39 small molecules released from islets. Benzoyl chloride derivatization of analyte molecules was used to impart retention and facilitate electrospray ionization efficiency. Separation was achieved on a 2.1 × 150 mm column packed with 2.7 μm core-shell C18 particles. Calibration curves showed excellent linearity between the concentration and analyte response, with relative standard deviations of the analyte responses below 15% and limits of detection from 0.01-40 nM. The method was applied to examine small molecules released from murine and human islets of Langerhans after static incubation and perfusion with glucose. Results showed a decrease in secretion rates with increasing glucose concentration for most of the analytes. Secretion rates were found to be higher in human islets compared to their murine counterpart. This method will be useful in understanding the roles of small molecules in biological systems.

Effects of subcutaneous tirzepatide versus placebo or semaglutide on pancreatic islet function and insulin sensitivity in adults with type 2 diabetes: a multicentre, randomised, double-blind, parallel-arm, phase 1 clinical trial

BACKGROUND

Tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist, shows a remarkable ability to lower blood glucose, enabling many patients with long-standing type 2 diabetes to achieve normoglycaemia. We aimed to understand the physiological mechanisms underlying the action of tirzepatide in type 2 diabetes.

METHODS

This multicentre, randomised, double-blind, parallel-arm, phase 1 study was done at two centres in Germany. Eligible patients were aged 20-74 years, had type 2 diabetes for at least 6 months, and were being treated with lifestyle advice and stable doses of metformin, with or without one additional stable dose of another oral antihyperglycaemic medicine, 3 months before study entry. Via a randomisation table, patients were randomly assigned (3:3:2) to subcutaneously receive either tirzepatide 15 mg, semaglutide 1 mg, or placebo once per week. Endpoint measurements were done at baseline and the last week of therapy (week 28). The primary endpoint was the effect of tirzepatide versus placebo on the change in clamp disposition index (combining measures of insulin secretion and sensitivity) from baseline to week 28 of treatment and was analysed in the pharmacodynamic analysis set, which comprised all randomly assigned participants who received at least one dose of a study drug and had evaluable pharmacodynamic data. Safety was analysed in the safety population, which comprised all randomly assigned participants who received at least one dose of a study drug. Secondary endpoints included the effect of tirzepatide versus semaglutide on the change in clamp disposition index from baseline to week 28 of treatment, glucose control, total insulin secretion rate, M value (insulin sensitivity), and fasting and postprandial glucagon concentrations. Exploratory endpoints included the change in fasting and postprandial insulin concentrations. This study is registered with ClinicalTrials.gov, NCT03951753, and is complete.

FINDINGS

Between June 28, 2019, and April 8, 2021, we screened 184 individuals and enrolled 117 participants, all of whom were included in the safety population (45 in the tirzepatide 15 mg group, 44 in the semaglutide 1 mg group, and 28 in the placebo group). Because of discontinuations and exclusions due to missing or unevaluable data, 39 patients in each treatment group and 24 patients in the placebo group comprised the pharmacodynamic analysis set. With tirzepatide, the clamp disposition index increased from a least squares mean of 0·3 pmol m^-2 L min^-2 kg^-1 (SE 0·03) at baseline by 1·9 pmol m^-2 L min^-2 kg^-1 (0·16) to total 2·3 pmol m^-2 L min^-2 kg^-1 (SE 0·16) at week 28 and, with placebo, the clamp disposition index did not change much from baseline (least squares mean at baseline 0·4 pmol m^-2 L min^-2 kg^-1 [SE 0·04]; change from baseline 0·0 pmol m^-2 L min^-2 kg^-1 [0·03]; least squares mean at week 28 0·3 [SE 0·03]; estimated treatment difference [ETD] tirzepatide vs placebo 1·92 [95% CI 1·59-2·24]; p<0·0001). The improvement with tirzepatide in clamp disposition index was significantly greater than with semaglutide (ETD 0·84 pmol m^-2 L min^-2 kg^-1 [95% CI 0·46-1·21]). This result reflected significant improvements in total insulin secretion rate (ETD 102·09 pmol min^-1 m^-2 [51·84-152·33]) and insulin sensitivity (ETD 1·52 mg min^-1 kg^-1 [0·53-2·52]) for tirzepatide versus semaglutide. On meal tolerance testing, tirzepatide significantly reduced glucose excursions (lower insulin and glucagon concentrations) compared with placebo, with effects on these variables being greater than with semaglutide. The safety profiles of tirzepatide and semaglutide were similar, with gastrointestinal adverse events being the most common (11 [24%], 13 [30%], and seven [25%] with nausea; nine [20%], 13 [30%], and six [21%] with diarrhoea; and three [7%], five [11%], and one [4%] with vomiting, for tirzepatide, semaglutide, and placebo, respectively). There were no deaths.

INTERPRETATION

The glycaemic efficacy of GIP/GLP-1 receptor agonist tirzepatide in type 2 diabetes results from concurrent improvements in key components of diabetes pathophysiology, namely β-cell function, insulin sensitivity, and glucagon secretion. These effects were large and help to explain the remarkable glucose-lowering ability of tirzepatide seen in phase 3 studies.

FUNDING

Eli Lilly.

Fatty acid synthase (Fasn) inhibits the expression levels of immune response genes via alteration of alternative splicing in islet cells

BACKGROUND

Increasing evidence has shown that fatty acid synthase (Fasn) is associated with diabetes mellitus (DM) and insulin resistance, however, it remains unclear how Fasn upregulation leads to dysregulation of energy homeostasis in islet cells. Consequently, uncovering the function of Fasn in islet cells. Consequently, uncovering the function of FASN in islet cells is immensely important for finding a treatment target.

AIM

In this study, we elucidated the biological function of Fasn on the target genes in a rat insulinoma INS-1 cell line.

METHODS

We created a Fasn overexpressing rat insulinoma cell line (Fasn-OE), and performed bulk RNA-sequencing (RNA-seq) experiments on Fasn-OE and INS-1 (control) cells. We first identified differentially expressed genes (DEGs) using Bioconductor package edgeR, and then discovered enriched gene ontology terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using the KEGG Orthology Based Annotation System (KOBAS) 2.0 web server. Furthermore, we identified alternative splicing events (ASEs) and regulated alternative splicing events (RASEs) by applying the ABLas pipeline. The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used for validation of selected differentially expressed genes (DEGs) and Fasn-regulated alternative splicing genes (RASGs).

RESULTS

In this study we found that Fasn overexpression led to significant changes of gene expression profiles, including downregulations of mRNA levels of immune related genes, including Bst2, Ddit3, Isg15, Mx2, Oas1a, Oasl, and RT1-S3 in INS-1 cell line. Furthermore, Fasn positively regulated the expression of transcription factors such as Fat1 and Ncl diabetes-related genes. Importantly, Fasn overexpression to result in alternative splicing events including in a metabolism-associated ATP binding protein mRNA Abcc5. In Gene Ontology analysis, the downregulated genes in Fasn-OE cells were mainly enriched in inflammatory response and innate immune response. In Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the downregulated genes were mainly enriched in TNF signaling pathway and cytokine-mediated signaling pathways.

CONCLUSIONS

Our findings showed that upregulation of Fasn may play a critical role in islet cell immunmetabolism via modifications of immune/inflammatory related genes on transcription and alternative splicing level, which provide novel insights into characterizing the function of Fasn in islet cell immunity and for the development of chemo/immune therapies.

Pharmacological management of patients undergoing total pancreatectomy with auto-islet transplantation

Chronic pancreatitis results in permanent parenchymal destruction of the pancreas gland leading to anatomical and physiological consequences for patients. Surgical management varies, and some patients require total pancreatectomy with autologous islet cell transplantation (TPIAT). Patients undergoing TPIAT require complex and diligent management after surgery. This encompasses the management of glucose control (endocrine function of the pancreas) and supplementing loss of exocrine function of the pancreas with digestive enzymes. Other areas of management include optimizing pain relief while reducing narcotic usage, providing antimicrobial prophylaxis, and reducing loss of islet cells by improving its integrity through anticoagulation and use of anti-inflammatory agents. Each aspect of care is unique to this population. However, comprehensive reviews on its pharmacological management are scarce. This review will discuss the available literature to date surrounding all aspects of pharmacological management of patients undergoing TPIAT.

Childhood Height Growth Rate Association With the Risk of Islet Autoimmunity and Development of Type 1 Diabetes

CONTEXT

Rapid growth has been suggested to promote islet autoimmunity and progression to type 1 diabetes (T1D). Childhood growth has not been analyzed separately from the infant growth period in most previous studies, but it may have distinct features due to differences between the stages of development.

OBJECTIVE

We aimed to analyze the association of childhood growth with development of islet autoimmunity and progression to T1D diagnosis in children 1 to 8 years of age.

METHODS

Longitudinal data of childhood growth and development of islet autoimmunity and T1D were analyzed in a prospective cohort study including 10 145 children from Finland, Germany, Sweden, and the United States, 1-8 years of age with at least 3 height and weight measurements and at least 1 measurement of islet autoantibodies. The primary outcome was the appearance of islet autoimmunity and progression from islet autoimmunity to T1D.

RESULTS

Rapid increase in height (cm/year) was associated with increased risk of seroconversion to glutamic acid decarboxylase autoantibody, insulin autoantibody, or insulinoma-like antigen-2 autoantibody (hazard ratio [HR] = 1.26 [95% CI = 1.05, 1.51] for 1-3 years of age and HR = 1.48 [95% CI = 1.28, 1.73] for >3 years of age). Furthermore, height rate was positively associated with development of T1D (HR = 1.80 [95% CI = 1.15, 2.81]) in the analyses from seroconversion with insulin autoantibody to diabetes.

CONCLUSION

Rapid height growth rate in childhood is associated with increased risk of islet autoimmunity and progression to T1D. Further work is needed to investigate the biological mechanism that may explain this association.

[Islet biomimetic microenvironment constructed by chitosan oligosaccharide protects islets from hypoxia-induced damage by reducing intracellular reactive oxygen species]

Objective

Gelatin methacryloyl (GelMA)/hyaluronic acid methacryloyl (HAMA)/chitosan oligosaccharide (COS) hydrogel was used to construct islet biomimetic microenvironment, and to explore the improvement effect of GelMA/HAMA/COS on islet activity and function under hypoxia.

Methods

Islets cultured on the tissue culture plate was set as the control group, on the GelMA/HAMA/COS hydrogel with COS concentrations of 0, 1, 5, 10, and 20 mg/mL respectively as the experimental groups. Scanning electron microscopy was used to observe the microscopic morphology, rheometer test to evaluate the gel-forming properties, contact angle to detect the hydrophilicity, and the biocompatibility was evaluated by the scaffold extract to L929 cells [using cell counting kit 8 (CCK-8) assay]. The islets were extracted from the pancreas of 8-week-old Sprague Dawley rats and the islet purity and function were identified by dithizone staining and glucose-stimulated insulin secretion (GSIS) assays, respectively. Islets were cultured under hypoxia (1%O 2) for 24, 48, and 72 hours, respectively. Calcein-acetyl methyl/propidium iodide (Calcein-AM/PI) staining was used to evaluate the effect of hypoxia on islet viability. Islets were cultured in GelMA/HAMA/COS hydrogels with different COS concentrations for 48 hours, and the reactive oxygen species kits were used to evaluate the antagonism of COS against islet reactive oxygen species production under normoxia (20%O 2) and hypoxia (1%O 2) conditions. Calcein-AM/PI staining was used to evaluate the effect of COS on islet activity under hypoxia (1%O 2) conditions. Islets were cultured in tissue culture plates (group A), GelMA/HAMA hydrogels (group B), and GelMA/HAMA/COS hydrogels (group C) for 48 hours, respectively. Immunofluorescence and GSIS assays were used to evaluate the effect of COS on islet activity under hypoxia (1%O 2) conditions, respectively.

Results

GelMA/HAMA/COS hydrogel had a porous structure, the rheometer test showed that it had good gel-forming properties, and the contact angle test showed good hydrophilicity. CCK-8 assay showed that the hydrogel in each group had good biocompatibility. The isolated rat islets were almost round, with high islet purity and insulin secretion ability. Islets were treated with hypoxia for 24, 48, and 72 hours, Calcein-AM/PI staining showed that the number of dead cells gradually increased with time, which were significantly higher than those in the non-hypoxia-treated group ( P<0.001). Reactive oxygen staining showed that GelMA/HAMA/COS hydrogels with different COS concentrations could antagonize the production of reactive oxygen under normal oxygen and hypoxia conditions, and this ability was positively correlated with COS concentration. Calcein-AM/PI staining indicated that GelMA/HAMA/COS hydrogels with different COS concentrations could improve islet viability under hypoxia conditions, and cell viability was positively correlated with COS concentration. Immunofluorescence staining showed that GelMA/HAMA/COS hydrogel could promote the expression of islet function-related genes under hypoxia conditions. GSIS assay results showed that the insulin secretion of islets in hypoxia condition of group C was significantly higher than that of groups B and C ( P<0.05).

Conclusion

GelMA/HAMA/COS hydrogel has good biocompatibility, promotes islet survival and function by inhibiting reactive oxygen species, and is an ideal carrier for building islet biomimetic microenvironment for islet culture and transplantation.

T-Cell Receptor/HLA Humanized Mice Reveal Reduced Tolerance and Increased Immunogenicity of Posttranslationally Modified GAD65 Epitope

Accumulating evidence supports a critical role for posttranslationally modified (PTM) islet neoantigens in type 1 diabetes. However, our understanding regarding thymic development and peripheral activation of PTM autoantigen-reactive T cells is still limited. Using HLA-DR4 humanized mice, we observed that deamidation of GAD65115-127 generates a more immunogenic epitope that recruits T cells with promiscuous recognition of both the deamidated and native epitopes and reduced frequency of regulatory T cells. Using humanized HLA/T-cell receptor (TCR) mice, we observed that TCRs reactive to the native or deamidated GAD65115-127 led to efficient development of CD4+ effector T cells; however, regulatory T-cell development was reduced in mice expressing the PTM-reactive TCR, which was partially restored with exogenous PTM peptide. Upon priming, both the native-specific and the deamidated-specific T cells accumulated in pancreatic islets, suggesting that both specificities can recognize endogenous GAD65 and contribute to anti-β-cell responses. Collectively, our observations in polyclonal and single TCR systems suggest that while effector T-cell responses can exhibit cross-reactivity between native and deamidated GAD65 epitopes, regulatory T-cell development is reduced in response to the deamidated epitope, pointing to regulatory T-cell development as a key mechanism for loss of tolerance to PTM antigenic targets.

Generation of human islet cell type-specific identity genesets

Generation of surrogate cells with stable functional identities is crucial for developing cell-based therapies. Efforts to produce insulin-secreting replacement cells to treat diabetes require reliable tools to assess islet cellular identity. Here, we conduct a thorough single-cell transcriptomics meta-analysis to identify robustly expressed markers used to build genesets describing the identity of human α-, β-, γ- and δ-cells. These genesets define islet cellular identities better than previously published genesets. We show their efficacy to outline cell identity changes and unravel some of their underlying genetic mechanisms, whether during embryonic pancreas development or in experimental setups aiming at developing glucose-responsive insulin-secreting cells, such as pluripotent stem-cell differentiation or in adult islet cell reprogramming protocols. These islet cell type-specific genesets represent valuable tools that accurately benchmark gain and loss in islet cell identity traits.

The roles of cell-cell and organ-organ crosstalk in the type 2 diabetes mellitus associated inflammatory microenvironment

Type 2 diabetes mellitus (T2DM) is a classic metaflammatory disease, and the inflammatory states of the pancreatic islet and insulin target organs have been well confirmed. However, abundant evidence demonstrates that there are countless connections between these organs in the presence of a low degree of inflammation. In this review, we focus on cell-cell crosstalk among local cells in the islet and organ-organ crosstalk among insulin-related organs. In contrast to that in acute inflammation, macrophages are the dominant immune cells causing inflammation in the islets and insulin target organs in T2DM. In the inflammatory microenvironment (IME) of the islet, cell-cell crosstalk involving local macrophage polarization and proinflammatory cytokine production impair insulin secretion by β-cells. Furthermore, organ-organ crosstalk, including the gut-brain-pancreas axis and interactions among insulin-related organs during inflammation, reduces insulin sensitivity and induces endocrine dysfunction. Therefore, this crosstalk ultimately results in a cascade leading to β-cell dysfunction. These findings could have broad implications for therapies aimed at treating T2DM.

Islet Encapsulation: New Developments for the Treatment of Type 1 Diabetes

Islet transplantation is a promising approach for the treatment of type 1 diabetes (T1D). Currently, clinical islet transplantation is limited by allo - and autoimmunity that may cause partial or complete loss of islet function within a short period of time, and long-term immunosuppression is required to prevent rejection. Encapsulation into semipermeable biomaterials provides a strategy that allows nutrients, oxygen and secreted hormones to diffuse through the membrane while blocking immune cells and the like out of the capsule, allowing long-term graft survival and avoiding long-term use of immunosuppression. In recent years, a variety of engineering strategies have been developed to improve the composition and properties of encapsulation materials and to explore the clinical practicality of islet cell transplantation from different sources. In particular, the encapsulation of porcine islet and the co-encapsulation of islet cells with other by-standing cells or active ingredients for promoting long-term functionality, attracted significant research efforts. Hydrogels have been widely used for cell encapsulation as well as other therapeutic applications including tissue engineering, cell carriers or drug delivery. Here, we review the current status of various hydrogel biomaterials, natural and synthetic, with particular focus on islet transplantation applications. Natural hydrophilic polymers include polysaccharides (starch, cellulose, alginic acid, hyaluronic acid, chitosan) and peptides (collagen, poly-L-lysine, poly-L-glutamic acid). Synthetic hydrophilic polymers include alcohol, acrylic acid and their derivatives [poly (acrylic acid), poly (methacrylic acid), poly(acrylamide)]. By understanding the advantages and disadvantages of materials from different sources and types, appropriate materials and encapsuling methods can be designed and selected as needed to improve the efficacy and duration of islet. Islet capsule transplantation is emerging as a promising future treatment for T1D.

Development of a scalable method to isolate subsets of stem cell-derived pancreatic islet cells

Cell replacement therapy using β cells derived from stem cells is a promising alternative to conventional diabetes treatment options. Although current differentiation methods produce glucose-responsive β cells, they can also yield populations of undesired endocrine progenitors and other proliferating cell types that might interfere with long-term islet function and safety of transplanted cells. Here, we describe the generation of an array of monoclonal antibodies against cell surface markers that selectively label stem cell-derived islet cells. A high-throughput screen identified promising candidates, including three clones that mark a high proportion of endocrine cells in differentiated cultures. A scalable magnetic sorting method was developed to enrich for human pluripotent stem cell (hPSC)-derived islet cells using these three antibodies, leading to the formation of islet-like clusters with improved glucose-stimulated insulin secretion and reduced growth upon transplantation. This strategy should facilitate large-scale production of functional islet clusters from stem cells for disease modeling and cell replacement therapy.

Development of scaffold-free vascularized pancreatic beta-islets in vitro models by the anchoring of cell lines to a bioligand-functionalized gelatine substrate

Bioengineered pancreatic β-islets have been widely advocated for the research and treatment of diabetes by offering both suitable cell culture models for the study of the pathology and the testing of new drugs and a therapy in those patients no longer responding to insulin administration and as an alternative to the shortage of donors for organ and islet transplantation. Unlike most of the studies published so far where pancreatic islets of pancreatic β-cells are encapsulated in hydrogels, this study demonstrate the formation of bioengineered pancreatic islets through cell anchoring to a gelatine-based biomaterial, PhenoDrive-Y, able to mimic the basement membrane of tissues. Through simple culture conditions, PhenoDrive-Y led human pancreatic β-cell lines and human umbilical endothelial cell lines to form organized structures closely resembling the natural vascularized pancreatic islets. When compared to gelatine, the cultures in presence of PhenoDrive-Y show higher degree of organization in tissue-like structures, a more pronounced endothelial sprouting and higher expression of typical cell markers. Noticeably, when challenged by hyperglycaemic conditions, the cells embedded in the PhenoDrive-Y assembled spheroids responded with higher levels of insulin production. In conclusion, the present work demonstrates the potential of PhenoDrive-Y as substrate for the development of bioengineered vascularized pancreatic islets and to be particularly suitable as a model for in vitro studies and testing of new therapeutics. Graphical abstract.

Quantification of Unmethylated Insulin DNA Using Methylation Sensitive Restriction Enzyme Digital Polymerase Chain Reaction

Assessment of specific β-cell death can be used to determine the quality and viability of pancreatic islets prior to transplantation and hence predict the suitability of the pancreas for isolation. Recently, several groups have demonstrated that unmethylated insulin (INS)-DNA is correlated to β-cell death in type 1 diabetes patients and during clinical islet isolation and subsequent transplantation. Here, we present a step-by-step protocol of our novel developed method for quantification of the relative amount of unmethylated INS-DNA using methylation sensitive restriction enzyme digital polymerase chain reaction This method provides a novel and sensitive way to quantify the relative amount of β-cell derived unmethylated INS-DNA in cellular lysate. We therefore suggest that this technique can be of value to reliably determine the purity of an islet preparation and may also serve as a measure of the quality of islets prior to transplantation measuring unmethylated INS-DNA as a reflection of the relative amount of lysed β-cells.

Identification and Validation of a New Peptide Targeting Pancreatic Beta Cells

Noninvasive targeted visualization of pancreatic beta cells or islets is becoming the focus of molecular imaging application in diabetes and islet transplantation studies. In this study, we aimed to produce the beta-cell-targeted peptide for molecular imaging of islet. We used phage display libraries to screen a beta-cell-targeted peptide, LNTPLKS, which was tagged with fluorescein isothiocyanate (FITC). This peptide was validated for targeting beta-cell with in vitro and in vivo studies. Immunocytochemistry (ICC) and fluorescence-activated cell sorting (FACS) analysis were used to validate the target specificity of the peptide. FITC-LNTPLKS displayed much higher fluorescence in beta cells vs. control cells in ICC. This discrimination was consistently observed using primary rodent islet. FACS analysis showed right shift of peak point in beta cells compared to control cells. The specific bind to in situ islet was verified by in vitro experiments using rodent and human pancreatic slices. The peptide also showed high affinity of islet grafts under the renal capsule. In the insulinoma animal model, we could find FITC-LNTPLKS accumulated specifically to the tumor, thus indicating a potential clinical application of molecular imaging of insulinoma. In conclusion, LNTPLKS showed a specific probe for beta-cells, which might be further utilized in targeted imaging/monitoring beta cells and theragnosis for beta-cells-related disease (diabetes, insulinoma, etc.).

Slow oscillations persist in pancreatic beta cells lacking phosphofructokinase M

Pulsatile insulin secretion by pancreatic beta cells is necessary for tight glucose control in the body. Glycolytic oscillations have been proposed as the mechanism for generating the electrical oscillations underlying pulsatile insulin secretion. The glycolytic enzyme 6-phosphofructokinase-1 (PFK) synthesizes fructose-1,6-bisphosphate (FBP) from fructose-6-phosphate. It has been proposed that the slow electrical and Ca2+ oscillations (periods of 3-5 min) observed in islets result from allosteric feedback activation of PFKM by FBP. Pancreatic beta cells express three PFK isozymes: PFKL, PFKM, and PFKP. A prior study of mice that were engineered to lack PFKM using a gene-trap strategy to delete Pfkm produced a mosaic reduction in global Pfkm expression, but the islets isolated from the mice still exhibited slow Ca2+ oscillations. However, these islets still expressed residual PFKM protein. Thus, to more fully test the hypothesis that beta cell PFKM is responsible for slow islet oscillations, we made a beta-cell-specific knockout mouse that completely lacked PFKM. While PFKM deletion resulted in subtle metabolic changes in vivo, islets that were isolated from these mice continued to exhibit slow oscillations in electrical activity, beta cell Ca2+ concentrations, and glycolysis, as measured using PKAR, an FBP reporter/biosensor. Furthermore, simulations obtained with a mathematical model of beta cell activity shows that slow oscillations can persist despite PFKM loss provided that one of the other PFK isoforms, such as PFKP, is present, even if its level of expression is unchanged. Thus, while we believe that PFKM may be the main regulator of slow oscillations in wild-type islets, PFKP can provide functional redundancy. Our model also suggests that PFKM likely dominates, in vivo, because it outcompetes PFKP with its higher FBP affinity and lower ATP affinity. We thus propose that isoform redundancy may rescue key physiological processes of the beta cell in the absence of certain critical genes.

Gain of Function of Malate Dehydrogenase 2 and Familial Hyperglycemia

CONTEXT

Genes causing familial forms of diabetes mellitus are only partially known.

OBJECTIVE

We set out to identify the genetic cause of hyperglycemia in multigenerational families with an apparent autosomal dominant form of adult-onset diabetes not due to mutations in known monogenic diabetes genes.

METHODS

Existing whole-exome sequencing (WES) data were used to identify exonic variants segregating with diabetes in 60 families from the United States and Italy. Functional studies were carried out in vitro (transduced MIN6-K8 cells) and in vivo (Caenorhabditis elegans) to assess the diabetogenic potential of 2 variants in the malate dehydrogenase 2 (MDH2) gene linked with hyperglycemia in 2 of the families.

RESULTS

A very rare mutation (p.Arg52Cys) in MDH2 strongly segregated with hyperglycemia in 1 family from the United States. An infrequent MDH2 missense variant (p.Val160Met) also showed disease cosegregation in a family from Italy, although with reduced penetrance. In silico, both Arg52Cys and Val160Met were shown to affect MDH2 protein structure and function. In transfected HepG2 cells, both variants significantly increased MDH2 enzymatic activity, thereby decreasing the NAD+/NADH ratio-a change known to affect insulin signaling and secretion. Stable expression of human wild-type MDH2 in MIN6-K8 cell lines enhanced glucose- and GLP-1-stimulated insulin secretion. This effect was blunted by the Cys52 or Met160 substitutions. Nematodes carrying equivalent changes at the orthologous positions of the mdh-2 gene showed impaired glucose-stimulated insulin secretion.

CONCLUSION

Our findings suggest a central role of MDH2 in human glucose homeostasis and indicate that gain of function variants in this gene may be involved in the etiology of familial forms of diabetes.

Microengineered Multi-Organoid System from hiPSCs to Recapitulate Human Liver-Islet Axis in Normal and Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a systematic multi-organ metabolic disease, which is characterized by the dynamic interplay among different organs. The increasing incidence of T2DM reflects an urgent need for the development of in vitro human-relevant models for disease study and drug therapy. Here, a new microfluidic multi-organoid system is developed that recapitulates the human liver-pancreatic islet axis in normal and disease states. The system contains two compartmentalized regions connected by a microchannel network, enabling 3D co-culture of human induced pluripotent stem cells (hiPSC)-derived liver and islet organoids for up to 30 days under circulatory perfusion conditions. The co-cultured liver and islet organoids exhibit favorable growth and improved tissue-specific functions. Transcriptional analyses reveal the activation of metabolically relevant signaling pathways in the co-cultured organoids. Notably, the co-culture system facilitates sensitive glucose-stimulated insulin secretion from islet organoids and increased glucose utilization in liver organoids by glucose tolerance tests. Both liver and islet organoids display mitochondrial dysfunction and decreased glucose transport capacity under high glucose conditions, which can be alleviated by metformin treatment. This novel multi-organoid system can recapitulate human-relevant liver-islet axis under both physiological and pathological conditions, providing a unique platform for future T2DM research and drug development.

Finding Eden - alternative transplantation sites for pancreatic islets

Pancreatic islets transplantation is an established treatment method for type 1 diabetic patients with the hypoglycemia unawareness syndrome in whom a therapy with modern technologies fails. Islet transplantation is most commonly done using an interventional radiology method: a tissue suspension of pancreatic islets is applied into a branch of the portal vein through a percutaneously installed catheter. Although being minimally invasive unlike pancreas organ transplant, this method is associated with many technical difficulties. Possible complications of the procedure include hemorrhage and portal vein thrombosis. Unlike their natural dispersed localization in exocrine pancreas, isolated pancreatic islets are exposed to hypoxia, toxins and immunosuppressive drugs in the liver parenchyma. Direct contact with the recipients blood causes an instant blood mediated inflammatory reaction (IBMIR) resulting in the death of more than half of the pancreatic islets shortly after their application. Therefore the size of the islet graft is often insufficient and a number of transplanted patients require administration of exogenous insulin. All of these are reasons for seeking an alternative transplantation site with more hospitable conditions for long-term islet survival. Various transplantation sites have been tested in experimental and clinical research. The advantages and disadvantages of some of them are summarized in this paper. Currently, transplantation into the greater omentum seems most promising, which has already been used in clinical practice at several institutions.

Detection of Glycosaminoglycans in Pancreatic Islets and Lymphoid Tissues

In this chapter, we describe the detection of the glycosaminoglycans hyaluronan and heparan sulfate in pancreatic islets and lymphoid tissues. The identification of hyaluronan in tissues is achieved by utilizing a highly specific hyaluronan binding protein (HABP) probe that interacts with hyaluronan in tissue sections. The HABP probe is prepared by enzymatic digestion of the chondroitin sulfate proteoglycan aggrecan which is present in bovine nasal cartilage and is then biotinylated in the presence of bound hyaluronan and the link protein. Hyaluronan is then removed by gel filtration chromatography. The biotinylated HABP-link protein complex is applied to tissue sections, and binding of the complex to tissue hyaluronan is visualized by enzymatic precipitation of chromogenic substrates.To determine hyaluronan content in tissues, tissues are first proteolytically digested to release hyaluronan from the macromolecular complexes that this molecule forms with other extracellular matrix constituents. Digested tissue is then incubated with HABP . The hyaluronan-HABP complexes are extracted, and the hyaluronan concentration in the tissue is determined using an ELISA-like assay.Historically, heparan sulfate was identified in tissue sections using the cationic dye Alcian blue and histochemistry based on the critical electrolyte concentration principle of differential staining of glycosaminoglycans using salt solutions. For both human and mouse pancreas sections, the current optimal method for detecting heparan sulfate is by indirect immunohistochemistry using a specific anti-heparan sulfate monoclonal antibody. A peroxidase-conjugated secondary antibody is then applied, and its binding to the anti-heparan sulfate antibody is visualized by oxidation and precipitation of a chromogenic substrate.